Cutting instrument having means for indicating usage



March 8, 1955 s. HENSEL ETAL 2,703,451

CUTTING INSTRUMENT HAVING MEANS FOR INDICATING USAGE Filed March 4, 1950 United States Patent CUTTING INSTRUMENT HAVING MEANS FOR INDICATING USAGE Herman Struve Hensel, New York, N. Y., and Joseph C. Fennelly, Ross, Calif.

Application March 4, 1950, Serial No. 147,616

13 Claims. (c1. 30-351 This invention relates in general to cutting instruments and it refers more particularly to instruments or the type having sharpened edges, such as knives, shears, razors, scaipels, braces, etc.

in the course or MS normal use, a cutting instrument of this character gradually loses its edge, and as the instrument becomes progressively duller, 1t ordinarily 1s oimcuit or impossible It) discern with me unaided eye ust wnen the cutting edge has reached the end of its practical useruiness; ror this reason instruments or the character indicated rrequentiy are used arter they have become too dun to do their work emcientiy, and, alternativeiy, the instruments often are resharpened (or discarueu and replaced) before they have reached the point where such is actually necessary.

It is an ob ect or the invention, therefore, to facilitate the determination of when, in the course of the normal use or a cutting instrument, its edge has become unpaired to the extent tnaat it should be replaced or sharpened. in other words, it is the principal object of the invention to provide a means or determining at any given time the extent of the use to WHICH. the cutting instrument already has been sub ected and, more particularly, to provide means giving an automatic visual indication of the extent of such use.

Another ob ect 18 to provide in connection with a multiedge blade (such as a double edge Gillette type razor blade) a means of telling easily which edge or edges have been used and which have not, and, in case that a plurality of edges have been used, which has been used the more.

Toward the foregoing ends, a feature of the invention resides in the application to the cutting edge of an instrument of a visible coating or tell-tale marking of such character as to undergo physical change as a result of the normal use of the instrument, and by such change, indicate the extent to which the cutting edge has been used.

Another feature of the invention is the provision of a tell-tale coating of the character indicated which will be eroded or worn away in the normal use of the cutting instrument, either through abrasive action alone or abrasive action in conjunction with softening of the coating by solvent or other chemical action occurring while the cutting edge is in use. The invention contemplates further the application to a given cutting edge of a plurality of coating substances having different wear characteristics whereby the coatings will be eroded, worn away or otherwise changed in an orderly succession to indicate different periods of use; the different coatings on a given cutting edge may be of the same or different colors to facilitate identification.

In connection with the use of a tell-tale marking on a cutting instrument as outlined hereinbefore, it is an object of the invention to prevent said marking from encouraging rusting of the cutting edge or otherwise adversely affecting the normal properties of the cutting instrument; and to this end it is a feature of the invention to use a coating material which is non-hygroscopic and which has rust inhibitive characteristics.

Particularly where the cutting instrument is a scalpel, razor blade or the like, a further object is to provide a use indicative coating which will not aggravate and preferably will counteract any septic conditions involved in the use of the instrument.

Other objects of the invention together with the fea- 2,703,451 Fatented Mar. 8, 1955 ice tures of novelty whereby the objects are achieved will appear in the course of the following description.

Although our invention is equally applicable to a wide variety or cutting instruments, it will for purposes of illustration be described in connection with a double edge razor blade of the Gillette type. Razor blades present a special problem in that the dulling which occurs in the course of shaving is virtually imperceptible to the naked eye, and, to the average user, a blade which has been employed in shaving to the extent that it is inadvisable to use it further, still does not appear visibly different than when the blade was new and unused. In other words, with the conventional razor blade it is impossible for the user by casual inspection to determine whether a blade should be discarded or whether it is capable of giving further satisfactory service. In the case of double edge razor blades of the Gillette type, there is the additional difiiculty that, assuming one edge is used for the first shave, it is impossible to determine on taking the blade up for the second shave, which edge was initially used; and thereafter in connection with subsequent shaves, it becomes increasingly difficult to determine which edge has been used the more. The choice of shaving edges after the initial shave therefore ordinarily is a haphazard matter, one edge often being used to excess while the other edge is used so little that it is capable of giving additional service at the time a blade is discarded.

In dealing with these problems by the provision of a tell-tale marking on the cutting edge of the razor blade, one must also face the problem of adapting the marking to the varying service life a given blade may have in the hands of different users. That is to say, because men differ considerably in the toughness of their beards and the manner of using the razor blade, the same blade may have a relatively long service life in the hands of one man, and a relatively short service life in the hands of another; the tell-tale marking obviously must be of such a character as to convey to any user the information necessary to assist him in determining when, in his own particular case, he should discard the blade or discontinue the use of a particular edge thereof. For these and other reasons, description of the invention in connection with its application to double edge razor blades is deemed to be peculiarly adapted to giving an understanding of the principles involved. It should be understood, however, that the tell-tale marking of razor blades discussed hereinafter is merely exemplary of the many similar uses of the invention that may be made, as will be readily apparent to those versed in the art.

In the accompanying drawings, which form a part of the specification and are to be read in conjunction therewith, and in which like refeernce numerals are employed to indicate like parts of the various views:

Fig. 1 is a plan view of a Gillette type double edge razor blade having a plurality of tell-tale stripes or hands of coating material applied to the plane surface and cutting edges of one side of the blade,

Fig. 2 is a similar view of the same blade showing the condition of the stripes after the initial use of the blade after a relatively short period of use,

Fig. 3 is a similar view of the blade showing the congitign of the stripes after a longer period of use of the Fig. 4 is a fragmentary cross sectional view of the blade taken along the line 4.-4 of Fig. 1 in the direction of the arrows showing the coating applied to one side of the blade, and

Fig. 5 is a fragmentary cross sectional view similar to Fig. 4 but showing the coating applied to both sides of the blade.

Referring more particularly to the drawings, the double ed e razor blade shown therein is of the conventional Gillette type. Generally rectangular in form with notched out corners, it has a body portion 10 of appreciable thickness with lateral non-cutti g ed es 11m and 11b and lon itudinal ed es 12 and 12b bevelled to form cutting surfaces. Applied to the face of the blade so that they extend to and overlao the bevelled cutting surfaces 12a and 12b are a pair of stripes or bands 13a and 13b of convenient width; these are located inwardly from the non-cutting edges 11a and 11b and are so interspaced as to prevent co-mingling of the coating substances. The character and constituency of the coating substances will be described more in detail presently.

For purposes of shaving, the blade is inserted in a con ventional razor, or blade holder, and used in conventional fashion. When it is inserted in the razor only the bevelled cutting edges 12:: and 1212 are exposed, the balance of the blade being covered and concealed by the parts of the razor between which the blade is clamped. If the tell-tale marking is applied only to one face of the blade as shown in Fig. 4, care must be taken in inserting the blade in the razor to position the blade so that the markings on the bevelled cutting edge will engage the face of the user; if both sides of the blade are marked as shown in Fig. 5, no such precaution is necessary inasmuch as the marking on one side will be in face-engaging position regardless of how the blade is inserted in the razor.

Preferably the coating material employed for stripe 13a is of lesser durability than the material comprising stripe 13b. Thus, for example, the former stripe may be of such a character that the portion on the bevelled cutting edge will, in the case of the average user, be rubbed, eroded or worn away in the course of shaving for the first time with a new blade (see Fig. 2) while stripe 13b may have a durability commensurate with the useful service life of the blade for the average user, so that its disappearance (see Fig. 3) is an indication that the associated cutting edge should no longer be employed. Quite obviously, a larger number of stripes may be employed, each difiering from the other in such a fashion as to give a more or less progressive indication of the degree of use to which the cutting edge has been subjected; alternatively if information as to the successive stages of use is not desired, a single stripe will suflice. Where a plurality of stripes are employed, we prefer to make them of a different color to facilitate identification, but this is not essential. Using a plurality of stripes of graded wear characteristics, the stripes being of different color or otherwise readily distinguishable from one another, any user will soon learn by experience that in his particular case the disappearance of a particular stripe indicates that the associated cutting edge will no longer give him satisfactory service.

In lieu of providing the blade with a plurality of stripes arranged side by side as shown in the drawings, it also is contemplated that one stripe be imposed upon another, forming a plurality of layers preferably of different color, which, by their successive disappearance, reveal to the use?1 at any given time how much the blade has been use It will be evident from the foregoing that the intermediate portions of our stripes do not wear away in use, the salient novelty of the invention residing in the application of a tell-tale marking material to the cutting edges where it is subject to erosion or abrasive removal in the course of the instruments use. We prefer to apply the coating material in the form of a stripe, however, both because of the enhanced appearance it gives the blade and also because of the ease of application. Conveniently, for example, the blades may be carried on a conveyor in a continuous succession under pads, rollers or other forms of applicators which transfer the coating material to the upper surfaces of the blades as they pass. When the end portion of a stripe has worn away in the course of use of a blade, the intermediate portion of the stripe still remaining assists the observer in quickly locating the particular portion of the cutting edge that previously bore the tell-tale marking; by thus flagging his attention to the disappearance of the latter, the likelihood of his absentmindedly overlooking the condition also is minimized.

Assuming, as will be true in most cases, that the coating medium is liquid or fluent at the time of application, it must, of course, dry or otherwise be cured after application, so that when the blade is first taken up for use the coating is in congealed or non-fluent state and bonded or adhered relatively securely to the blade, whereby it will resist removal in the course of the ordinary handling that occurs in preparing the blade for shaving. The telltale marking must not, in other words, be wipable from the blade, but rather must be somewhat paint-like in character, having sufficient inherent integrity and cohesive toughness or tenacity to make it a semi-permanent part of the blade, yet subject to attrition or abrasive removal upon normal use of the blade for shaving, as described hereinbefore.

The coating substance employed preferably is one containing a 111st inhibiting agent. In connection with razor blades and kindred instruments, it is important that the coating have no adverse etfect on the skin of the user and we prefer, therefore, to incorporate in it a suitable antiseptic for preventing septic conditions.

The action by which the removal of a given marking material is accomplished is subject to wide variation depending upon the use to be made of the instrument which is thus marked. Thus the character of the coating may be such that the wear or erosion thereof is purely due to abrasive action. On the other hand, it may be of such composition that the material is conditioned for abrasive removal by the water, lather or other beard softener to which it is subjected in the course of use; that is to say, materials may be employed for the different stripes which differ from one another, for example, in their water solubility so that the coatings of higher solubility are rendered removable first and those of lower solubility are rendered removable only upon longer use of the cutting edge.

It is contemplated that one such coating substance may be formulated as a colloidal solution which will dissolve at the first application of an agent wetting the surface of the cutting edge. (In the case of a razor blade, this naturally would take place on the first shave.) A second coating of greater water resistance to indicate a subsequent use of the same cutting edge can comprise a cellulose mixture. Other coatings can be formulated in like fashion to meet the requirements for indicating different periods of use.

Referring to the stripes 13a and 13b in the drawings, the following are suggested as typical compositions suitable for the respective coating, the relative proportions of the various constituents being as indicated:

Tests employing these compositions on a razor blade indicate that coating 13a will be removed by the first use of the blade and coating 13b remains intact through approximately the first three uses of the blade but is removed on the fourth use which, in the case of the average shave, represents the maximum amount of use which could be obtained from one edge of the blade under consideration. It should be understood, of course, that the foregoing compositions are merely exemplary and should in no way be construed as limiting the invention inasmuch as innumerable other coating materials may be employed quite as satisfactorily.

From the foregoing it will be seen that our invention is well adapted to attain the ends and objects hereinbefore set forth together with other advantages which are obvious and which are inherent to the invention.

It will be understood that certain features and subcombinations are of utility and may be employed without reference to other features and subcombinations. This is contemplated by and within the scope of the claims.

Inasmuch as many possible embodiments may be made of the invention without departing from the scope thereof, it is to be understood that all matter herein set forth or shown in the drawings is to be interpreted as illustrative and not in a limiting sense.

Having thus described our invention, we claim:

1. A new article of manufacture comprising a tool having a cutting edge, a plurality of non-fluent coatings on the cutting edge, each coating subject to attrition from abrasive action occurring through the normal use of the tool for cutting purposes, and said coatings differing from one another in color and in resistance to wear.

2. A new article of manufacture comprising a tool having a cutting edge of appreciable length, and nonfluent coatings at a plurality of separated points along said edge, each of said coatings subject to attrition from abrasive action occurring through the normal use of the tool for cutting purposes, and the coatings at the different points along the length of said edge having different resistance to wear.

3. An article as in claim 2 wherein said coatings differ from one another in color.

4. A razor blade having visible surface coatings at a plurality of separated points along the cutting edge, said coatings differing from one another in their water solubility whereby they are subject to attrition at different rates during shaving due to abrasive action in the presence of the water used in shaving.

5. A razor blade having a cutting edge of appreciable length, a restricted portion of the length of said cutting edge having thereon a shaving usage telltale, said telltale comprising an easily visible paint-like coating subject to attrition due to abrasive action occurring through normal use of the blade in shaving, the portion of the cutting edge immediately adjacent said coated portion being free of said coating to contrast therewith and thus enhance the visibility of the coated portion, said coating being substantially immune to attrition while in a dry condition but has a predetermined water solubility rendering it susceptible to attrition in the presence of the water normally used in shaving.

6. A razor blade having a cutting edge of appreciable length, a restricted portion of the length of said cutting edge having thereon a shaving usage telltale, said telltale comprising an easily visible paint-like coating subject to attrition due to abrasive action occurring through normal use of the blade in shaving, the portion of the cutting edge immediately adjacent said coated portion being free of said coating to contrast therewith and thus enhance the visibility of the coated portion, said coating in its natural state being hard and substantially immune to attrition, said coating being subject to softening in the presence of the shaving cream normally used in shaving.

7. A double-edge razor blade having on one face thereof an easily visible surface stripe extending across the blade from one cutting edge to the other, said stripe comprising a non-fluent coating subject to attrition at the ends of the stripe due to abrasive action occurring through normal use of the blade in shaving, the width of said stripe being less than the length of the cutting edges whereby each end of the stripe covers but a restricted portion of one cutting edge.

8. A double-edge razor blade having on one face thereof a plurality of laterally spaced surface stripes extending across the blade from one cutting edge to the other, each stripe comprising a non-fluent coating subject to attrition at the ends of the stripe due to abrasive action occurring through normal use of the blade in shaving, and the coatings forming the different ones of said stripes differing from one another in their resistance to wear.

. 9. A razor blade as in 8 wherein the coatings forming the different stripes differ from one another in color.

10. A double-edge razor blade having on one face thereof a plurality of laterally spaced surface stripes extending across the blade from one cutting edge to the other, each stripe comprising an easily visible non-fluent coating, and the coatings forming the different ones of said stripes differing from one another in their water solubility whereby the ends of the respective stripes are subject to attrition at different rates during shaving due to abrasive action in the presence of the water used in shaving.

11. A razor blade as in claim 10 wherein the coatings foil'ming the different stripes differ from one another in co or.

12. A new article of manufacture comprising a tool having a cutting edge, a multi-layer cured paint-like coating on the cutting edge subject to attrition from abrasive action occurring through the normal use of the tool for cutting purposes, the different layers of said coating differing from one another in color.

13. An article as in claim 12 wherein the different ones of said layers differ from each other in their resistance to wear.

References Cited in the file of this patent UNITED STATES PATENTS 1,846,622 Thompson Feb. 23, 1932 2,058,366 Steele Oct. 20, 1936 2,239,526 Muros Apr. 22, 1941 2,292,417 Wetherbee Aug. 11, 1942 2,326,774 Freedman Aug. 17, 1943 FOREIGN PATENTS 133,093 Austria Apr. 25, 1953 330,865 Great Britain June 19, 1930 

